Some animal that could not be classified as a chicken was produced offspring via eggs. During sexual reproduction and random gene mutation, the animal that emerged from the egg is what we classify as a chicken.

The above theory is more plausible to me then the idea that chickens produced offspring by live birth and then evolved egg producing. On the other hand, it just delays the question to: Which came first - the animal(s) that gave birth to the chicken or the egg that created that animal(s).

For the record, I am a Christian with a non-traditional perspective.